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Light-Driven Raman Coherence as a Nonthermal Route to Ultrafast Topology Switching in a Dirac Semimetal

C. Vaswani, L.-L. Wang, D. H. Mudiyanselage, Q. Li, P. M. Lozano, G. D. Gu, D. Cheng, B. Song, L. Luo, R. H. J. Kim, C. Huang, Z. Liu, M. Mootz, I. E. Perakis, Y. Yao, K. M. Ho, and J. Wang
Phys. Rev. X 10, 021013 – Published 17 April 2020
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Abstract

A grand challenge underlies the entire field of topology-enabled quantum logic and information science: how to establish topological control principles driven by quantum coherence and understand the time dependence of such periodic driving. Here we demonstrate a few-cycle THz-pulse-induced phase transition in a Dirac semimetal ZrTe5 that is periodically driven by vibrational coherence due to excitation of the lowest Raman active mode. Above a critical THz-pump field threshold, there emerges a long-lived metastable phase, approximately 100 ps, with unique Raman phonon-assisted topological switching dynamics absent for optical pumping. The switching also manifests itself by distinct features: nonthermal spectral shape, relaxation slowing near the Lifshitz transition where the critical Dirac point occurs, and diminishing signals at the same temperature that the Berry-curvature-induced anomalous Hall effect magnetoresistance vanishes. These results, together with first-principles modeling, identify a mode-selective Raman coupling that drives the system from strong to weak topological insulators with a Dirac semimetal phase established at a critical atomic displacement controlled by the phonon coherent pumping. Harnessing of vibrational coherence can be extended to steer symmetry-breaking transitions, i.e., Dirac to Weyl ones, with implications for THz topological quantum gate and error correction applications.

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  • Received 21 November 2019
  • Revised 30 January 2020
  • Accepted 5 March 2020

DOI:https://doi.org/10.1103/PhysRevX.10.021013

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

C. Vaswani1, L.-L. Wang1, D. H. Mudiyanselage1, Q. Li2, P. M. Lozano2, G. D. Gu2, D. Cheng1, B. Song1, L. Luo1, R. H. J. Kim1, C. Huang1, Z. Liu1, M. Mootz3, I. E. Perakis3, Y. Yao1, K. M. Ho1, and J. Wang1,*

  • 1Department of Physics and Astronomy and Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA
  • 2Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
  • 3Department of Physics, University of Alabama at Birmingham, Birmingham, Alabama 35294-1170, USA

  • *Corresponding author. jwang@ameslab.gov

Popular Summary

Wide-scale adoption of quantum computing requires building devices in which fragile quantum states are protected from their noisy environments. One approach is through the development of topological quantum computation, in which qubits are based on “symmetry-protected” quasiparticles that are theoretically immune to noise. However, the field faces a grand challenge: how to establish topological control principles driven by quantum coherence and understand the time-dependent effects of the necessary periodic driving. Our study is the first demonstration of such coherent control of topology in a Dirac semimetal, an exotic material that exhibits extreme sensitivity because of its proximity to a broad range of topological phases. This principle supports a nearly dissipationless topological switching and at the ultimate terahertz speed of operation, i.e., a clock rate of 1012 Hz.

We achieve this phase transition by a new light-based quantum-control principle known as mode-selective Raman phonon coherent oscillations—light-induced periodic motions of atoms about their equilibrium position. These extra “quantum fluctuations” induce transitions between states with different topological orders. An analogy of such dynamic switching is the periodically driven Kapitza pendulum, which can transition to a new inverted, yet stable, orientation, thus imposing a sufficiently high-frequency vibration of its pivot point. We show that this principle is applicable in a broad range of topological phases, from strong topological insulators to Dirac semimetals. This coherent control is also in stark contrast to any equilibrium tuning methods such as chemical substitution and static fields, which have a much slower speed and higher energy cost.

Our work opens a new arena of light-wave-speed topological electronics and phase transitions controlled by quantum coherence that will be useful in the development of future quantum-computing strategies and electronics with high speed and low energy consumption.

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Vol. 10, Iss. 2 — April - June 2020

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